Question

The half-life period of a first order reaction is 10 minutes. Starting with initial concentration 12 M, the rate after 20 minutes is
A. `0.693 xx 3 M min^(-1)`
B. `0.0693 xx 4 M min^(-1)`
C. `0.0693 M min^(-1)`
D. `0.0693 xx 3 M min^(-1)`

Answer 1

Correct Answer - D
d) `underset("Initial conc")(12M)overset(t_(1//2))to6Moverset(t_(1//2))tounderset("Final conc.")(3M)`
`t_(1//2) = 10`min , k = `(0.693)/(10)=0.0693 min^(-1)`
After 20 minutes, the concentration will be 3M.
rate =k[3M] = `(0.0693 min^(-1) xx 3M)`s